It is known from the prior art that alkyl(amino)dialkoxysilanes can be prepared in relatively pure form. However, the known methods involve difficult syntheses in which the reaction parameters must be carefully controlled to minimize unwanted by-products and concomitant separation and activity problems. For example, U.S. Pat. No. 4,491,669 discloses the different approaches of (1) alcoholysis of a chlorosilane compound to replace one or more of the chlorine groups with alkoxy or aryloxy groups, and then replacing the remaining chlorine by reaction with a twice molar excess of an amino compound; and (2) by replacing one or more amino groups of a multiple-amine substituted silane compound by reaction with an alcohol. These reactions can be represented by the following simplified general equations: ##STR1## where: R is hydrogen, a short chain alkyl or alkenyl group of up to eight carbon atoms or an aryl, such as phenyl;
R" and R'" are separately either hydrogen, a short chain alkyl or aryl, at least one being other than hydrogen; PA1 R' is a short chain alkyl or aryl; and PA1 m and n are integers. PA1 R.sup.1 and R.sup.2 are alkyl radicals of 1 to 6 carbon atoms and one of them can be hydrogen; PA1 R.sup.3 is an alkyl radical of 1-6 carbon atoms with methyl being preferred; and PA1 X is a halogen atom selected from Cl, Br or I, with Cl being preferred.
These compounds have also been prepared by the reaction of an alkylamine with alkoxychlorosilane compounds. The reaction (1B) of an alkyltrichlorosilane with two equivalents of alcohol followed by displacement of the remaining chloride by an amine is of limited interest as a commercial process because of the difficulty in forming the alkylchlorodialkoxysilane (1A) without also forming alkyltrialkoxysilane and alkyldichloroalkoxysilane. This mixture of products affects the efficiency of the next reaction (1B). Similarly, the selective alcoholysis of an alkyltri(amino) silane (2) also results in a mixture of products and the attendant separation problems.
A process for producing alkyl(amino)dialkoxysilanes using a Grignard reagent in diethyl ether solvent is disclosed in Japanese patent application HEI 9[1997]-40714/HEI 7[1995]-192793. However, no yields were reported in any of the purported working examples of that application. When replication of the reported results was attempted, it was found that the piperidinomagnesium chloride salt and a diethylaminomagnesium chloride salt, (both prepared in accordance with the procedure described in Example 11 of the Japanese reference), were both insoluble in the diethyl ether. A slurry of the piperidinomagnesium chloride in diethyl ether was reacted with methyltrimethoxysilane to produce the expected methyl(piperidino)dimethoxysilane. This reaction proceeded very slowly. The 75% yield of crude product obtained is equivalent to about a 65% isolated yield (estimated) of the purified product. The results of the replication lead one of ordinary skill in the art to conclude that the processes described in this Japanese application would not be economically practical for use in a scaled-up, commercial process due to the relatively low yield of the desired product coupled with extremely long reaction time.
In view of these limitations of the prior art, it is a principal object of the present invention to provide an improved one-step process starting from alkylalkoxysilanes for producing alkyl(amino)dialkoxysilanes of high purity and in yields greater than those attained by the prior art. In the context of the description of the invention in this application, it is to be understood that the term "alkyl" means alkyl, arylalkyl and aryl substituents.
Another principal object of the invention is to provide an improved process that is practical and economical for the commercial production of the desired products by minimizing the production of unwanted by-products and the concommitant separation and activity problems.
It is another object of the invention to provide an improved process for producing alkyl(amino)dialkoxysilanes at temperatures ranging from 25-75.degree. C.
An additional object of the invention is to provide an improved process for producing alkyl(amino)dialkoxysilanes in which the by-products are an alkane and a magnesium alkoxychloride salt which are non-hazardous and can be disposed of economically.
Still another object of the invention is to provide a process for producing alkyl(amino)dialkoxysilanes in which the solvent is recycled for use in the process.
A further object of the invention is to provide a process for producing specified alkyl(amino)dialkoxysilane compounds for use as stereoregulators in .alpha.-olefin polymerization catalysts.